1. Field of the Invention
The present invention relates to post tensioning concrete anchor assemblies and, more particularly, to an anchor plate assembly for post tensioning structures.
2. History of the Prior Art
The technology for the post tensioning concrete structures is well established. Anchor plate assemblies are generally utilized for the securement of post tensioning filaments or tendons that extend through a body of concrete. The tendons, which are generally steel cables, impart compressive loads to, and enhance the strength of, the concrete in a manner that is sometimes not economically and/or mechanically possible with conventional rebar construction. Anchor assemblies on opposite end of the tendons are critical to this technique, and the effectiveness of the interconnection between the anchor plates and the tendons, as well as the sealing of the assembly, is critical to the effective life span of the construction.
Corrosion is an important consideration in the utilization of post tensioning assemblies. It is well known that corrosion can cause deterioration in the anchor plate assemblies and this can result in a deleterious effect on the ultimate strength of the concrete. It is for this reason that the steel fibers that generally comprise the post tensioning cables are usually placed within a plastic sheath which extends through the slab. This sheath must, however, be cut off short of its connection to the anchor assemblies in order to allow the anchor wedges thereof to directly engage the steel fibers. The exposed fibers must, however, be subsequently covered in some respect in order to prevent the problems of subsequent corrosion.
In order to facilitate sealing of post tensioning cables and the ultimate elimination of moisture therearound, grease is often used in or around the caps and tubular members that are generally used to cover the plate extending around the anchor plate. A thorough description of such prior art approaches, as well as related innovations in anchor plate assemblies and improvements therein, is set forth and shown in U.S. Pat. No. 4,821,474 which issued to Alan Rodriguez on Apr. 18, 1989. In this patent, an anchor plate assembly of a type utilized in post tensioning configurations is set forth and described in detail. Likewise other prior art patents also referenced in this particular patent include U.S. Pat. No. 4,363,462 to Wlodkowsi, et al., issuing on Dec. 14, 1982 and U.S. Pat. No. 4,121,325 to Bruinette, et al., issuing in 1978.
The above mentioned prior art references teach a variety of approaches to post tensioning anchor assemblies for prestressed concrete. As stated in certain ones of those references, the elimination of corrosion of the post tensioning cables and in the anchor plate assemblies is a primary consideration in order to prevent failure in the tensioning cable. The assembly of sealing caps and "stackable" tubular members on opposite sides of the anchor plate itself is well known in this particular technology. It would be an advantage however to provide an improved method of securing the cap and the tendon covering tubular members to the anchor plate for purposes of both shipping and handling of the anchor plate assembly as well as its subsequent use.
The present invention provides such an advance over the prior art by providing a post tensioning anchor plate assembly that utilizes aligned, cylindrical portions, or bosses, each being formed with a recess constructed in the outer cylindrical surfaces thereof. The recess or groove, is used to matingly engage protruding lips formed inside the plastic cap and inside the tubular connection member specifically adapted for connection to opposite sides of the anchor plate. In this manner, both the cap and the tubular connection member (or adapter) can be reliably secured to, and effectively sealed with, the anchor plate enhancing the reliability thereof. A compression ring is also provided for securement around the cap and tubular connection member to enhance the sealing thereof.